Investigating the link between vomeronasalitis and aggression

The vomeronasal organ is a sensory organ present in many species that contacts the nasal and oral cavities. It is responsible for receiving chemical signals from other cats in the form of pheromones. Many studies in several species have demonstrated that removal or obstruction of the vomeronasal organ causes a decrease in social and reproductive behaviour. To date, no studies in cats have reported spontaneously occurring vomeronasal disease.

The purpose of this study was to determine if naturally occurring inflammatory changes to the vomeronasal organ correlate with increased aggression in cats.

Study subjects included 20 cats (10 male and 10 female) from multi-cat households presenting for post mortem examination. 6 animals had been euthanized due to severe aggression, while 14 died of other organic causes. Vomeronasal organs were collected and prepared for histological exam and classified as having acute, chronic, or no inflammatory changes. Sensory and non-sensory tissues were considered separately. Owners also filled out a questionnaire at the time of their cat’s death regarding aggressive behaviours.

14 cats had evidence of vomeronasal inflammation, all of which were chronic. Various sub classifications of inflammation were identified. Most cats had inflammation of both sensory and non-sensory tissue, however a small amount were limited to one or the other. 25% of cats had a history of aggressive behaviour to other cats, and 40% demonstrated aggression to humans. Statistical analysis of the data was preformed.

Results of this study found a significant correlation between vomeronasalitis of the sensory tissue and aggression with other cats. Inflammation of non sensory tissue was not associated with increased aggression. There was no correlation between any type of inflammation and aggression to humans, or with any other factor (ie sex, age, etc).

There are multiple potential causes of vomeronasal inflammation. This may occur secondary to infection or inflammation of the nasal or oral cavity, as a result of systemic diseases (such as FIP). The consequence of this inflammation is likely an impaired ability to receive and interpret chemical signals from other cats. It logically makes sense that this would result in increased aggression with other cats (as they rely on pheromone signalling) but not with humans (who do not rely on pheromones to communicate with cats).

This study has several drawbacks including a small sample size and a lack of detail involving underlying causes of inflammation or types and reasons for aggression. Despite these drawbacks, this study provides a foundation for further work on the relationship between vomeronasal disease and intra-cat aggression. This may pave the way for further treatment options for intra-cat aggression that may treat the underlying cause rather than the symptoms.